This application claims priority to European Application No. 00 810 866.4 filed Sep. 21, 2000 and herein incorporated by reference in its entirety.
1. Field of the Invention
This invention relates to a perimeter for testing the field of vision of a patient, the device having a head restraint for positioning the head of a patient, a control panel and a unit base on which an optical system with an eyepiece is located, in front of which the patient""s head is to be positioned.
2. Description of the Prior Art
Automatic perimeters for the testing of the field of vision are described in the prior art and are used both in research and in practice for routine examinations. A perimeter of this type is commercially available under the trade name OCTOPUS, for example. With this perimeter, the sensitivity of the retina to differences in light levels is determined at different locations in the field of vision using a computer-controlled process. For these examinations, it is essential that the patient hold his head in a predetermined position that is symmetrical for the left eye and the right eye with reference to a viewing axis. During this examination, the patient sits in front of the perimeter and by means of a head restraint, which consists essentially of a chin rest and a head rest, the head and the eye being examined are positioned in front of the eyepiece. The person conducting the tests sits opposite the person being examined and operates the perimeter by means of a control panel which is attached to the perimeter.
U.S. Pat. No. 5,125,731 describes a perimeter of the type described above in which the head rest and chin rest for the positioning of the patient""s head and eye can be adjusted during the examination. However, this process of precisely positioning the patient""s head interferes with the patient""s concentration and inevitably has a negative effect on the length of the examination and the quality of the examination results. Perimeters in general are also quite bulky, and it is frequently difficult to position them appropriately in an examination room because consideration has to be given to the fact that suitable seated positions are required for the patient and for the operator respectively.
An object of the invention is to create a perimeter for examining the field of vision that eliminates or reduces the disadvantages described above and that also delivers accurate examination results because the patient is in a comfortable position and the device is simple and easy to operate.
The invention teaches that this object can be accomplished in a perimeter of the type described above but in which the optical system is movably mounted on the unit base and can be adjusted in the vertical and horizontal direction by means of a drive.
On the perimeter of the invention, the optical system is movably mounted on the unit base and can be adjusted with respect to the control panel. It is thereby possible to freely select the position between the patient and the operator. The operator and the patient no longer necessarily have to sit opposite each other or at another defined angle; the positions of the operator and the patient can be selected without restrictions, which is advantageous above all in small spaces. An additional advantage of the perimeter of the invention is that for the precise positioning of the eye being examined in front of the eyepiece, the optical unit can be tracked in all directions. Because in this case it is no longer necessary to adjust the head restraint, the patient""s concentration is not disrupted during a precise positioning of this type.
Additional advantageous characteristics of the invention are disclosed in the dependent claims, in the following portion of the description and in the accompanying drawings.